The goal is to validate a battery of biologic markers of prenatal exposure to organophosphates and other non-persistent pesticides (carbamates and pyrethroids). The research is needed to facilitate evaluation of health impacts associated with exposures during pregnancy, given the widespread residential use of these pesticides. Experimental data have linked prenatal organophosphate exposure to adverse neurocognitive development. Exposures during the spurt in brain growth (which begins in humans during the 3rd trimester) appear particularly deleterious. Prenatal exposures to pyrethroids and carbamates may also have neurotoxic effects. However, epidemiologic research on these relationships have been hampered by the lack of reliable dosimeters. No prior studies have validated biomarkers specific to prenatal exposures. The proposed research builds on a STAR grant recently awarded by the U.S. EPA to validate the measurement of non-persistent pesticides in postpartum meconium. The applicants are proposing to validate a large battery of additional biomarkers within the same study design at relatively little additional cost. Biomarkers to be validated are pesticide levels in maternal urine samples collected every 2 weeks during the 3rd trimester and pesticide levels in biologic samples collected at delivery (urine and blood samples from mothers and newborns). The cohort will consist of 100 pregnant African American and Dominican women from Northern Manhattan and South Bronx. Residential pesticide use is widespread among this minority population. Pesticide levels in indoor air monitored continuously at the woman's residence during the 3rd trimester (adjusting for the amount of time the women has spent in the home and controlled for non-residential exposures) will provide the "gold standard" for validation purposes. Questionnaire data will include detailed information on pesticide use during each trimester of pregnancy, as well as the amount of time the woman has spent in the home and history of non-residential exposures during the monitoring. The study will compare the degree to which pesticide levels in the biologic samples are associated with residential exposures and will determine the sensitivity and specificity of these biomarkers, singly and in combination, in order to select the battery of biologic markers that has the highest predictive power of prenatal exposure.